Study On Protection Of QingZang Railway Distribution System With Long Distance Transmission Lines

With the further development of the West, the construction of the Qingzang railway is carried on vigorously. Because the special geological and climatic surrounding along the line causes the power-supply difficulty, an extra-long distance power distribution system is thus produced, with the longest 330km. To assure the quality, a trans-region power-supply system is necessary, with compensation equipments in series. And because of the complexity of the surrounding, the transition resistance is impossible to predetermine. Therefore, in order to act correctly and timely, a reasonable protection scheme is put forward to avoid the influences of the transition resistance and the in-series compensation equipment.First, the paper starts from status quo of the configuration, characteristics, running mode and relay protection in the railway distribution system, the models of Tuotuo-river loading area and Natuo line are set up according to the running situation and various parameters along Qingzang line.Second, the failure simulation is carried out for the whole Qingzang power line. The current, voltage, impedance angle, the line's impedance and their varying trend are studied, in preparation for the discussion of the protection-configuring scheme.Third, aiming at the two modes in Qingzang line, including the normal and the trans-region power-supply, several protection-configuring schemes are mainly discussed. (1) With current protection, the simulation shows: the influence of the transition resistance can't be avoided in normal mode; and both negative influences can't be eliminated in trans-region mode. That is, the selectivity of the protection can't be guaranteed in both modes. Obviously, Current protection is not fit for Qingzang power line. (2) The protection principle on the basis of impedance angle is analyzed. This method also can't be adopted because the impedance angle has no obvious changing scope before and after the failure. (3) With impedance protection, the simulation shows: the influence of the transition resistance can be avoided in normal mode, the protection acts correctly; and the influences of the transition resistance can be eliminated, but that of the in-series compensation capacitances can't. False action occurred in specific sections.Furthermore, two perfection methods of impedance protection are proposed: (1)...